1. Field of the Invention
This invention relates to a suspension system for vehicles and, more particularly, a strut mounting structure.
2. Description of the Prior Art
In general, in a vehicle suspension system, a strut device comprising a damper member and a spring member is arranged between a wheel support member and a body side member for controlling the oscillation of a wheel of the vehicle.
FIG. 6 shows a well known strut mounting structure. In FIG. 6, a lower part 51 of a strut is connected to a wheel support member. A first rubber bushing 53 connects an upper part 52 of the strut to the body side member 54. A lower spring seal 56 connected to the lower part 51 of the strut supports a lower part of a coil spring 55 located around the strut. An upper spring seal 58 connected to a second rubber bushing 57 supports an upper part of the coil spring 55. The first rubber bushing is supported by a case 60 bolted to the body side member 54.
The compressibility (hardness) of the first rubber bushing 53 is usually arranged in accordance with a non-loaded condition of the vehicle. When the wheel is bumped in a loaded condition, the strut generates a clamping force in the same way as in the non-loaded condition. That is, first the rubber bushing 53 deforms, and then the strut generates a damping force, after some delay. This delay or damping timing does not spoil the comfort of a ride and cornering stability in the non-loaded condition, since the suspension is moved through relatively small oscillations due to the light weight of the vehicle. However, in a loaded condition, the suspension tends to move through great oscillations due to the heavy weight of the vehicle in the loaded condition. During the delay in the damping timing, in other words, a predetermined time until the damping force acts against suspension movement, the suspension is free to oscillate. Therefore, this predetermined delay of damping timing badly affects the vehicle as the amount of weight in the loaded condition increases, because a great oscillation will occur before the damper acts in the loaded condition.